Styphnolobium japonicum agglutinin (SJA) is affinity purified from Japanese pagoda tree seeds. It consists of two subunits. The subunits can be separated into two subfractions, a D-galactose/N-acetyl-D-galactosamine specific lectin (B-SJA-I) and a D-mannose/D-glucose specific lectin (B-SJA-II). SJA has an isoelectric point between pH 4.9 and pH 5.6 and a carbohydrate specificity towards βGalNAc. This lectin elutes with the sugar GalNAc.
SJA agglutinates all blood group types but has greater affinity for A erythrocytes than of B types, than of O (-SA) types. Binding experiments of the lectin with frozen sections of human kidneys shows specific binding to the endothelia in specimens from blood groups B or AB, thus indicating a D-galactose/N-acetyl-D-galactosamine receptor specificity. SJA lacks mitogenic and immune-suppressive activity.
Alkaline phosphatase (AP) is conjugated to Styphnolobium japonicum Lectin (SJA) to show the binding of SJA in many applications including Western blotting and ELISA. Alkaline phosphatase is a large protein (140 kDa) that catalyzes the hydrolysis of phosphate groups from a substrate resulting in a colored or fluorescent product. The optimal enzymatic activity of this protein is between pH 8 and 10, and its reaction rate remains linear, improving sensitivity over time.